HAND-ARM VIBRATION IN
FOUNDRIES
© Crown copyright 2001Applications for reproduction should be madein writing to: Copyright Unit, Her Majesty'sStationery Office, St Clements House, 2-16 Colegate, Norwich NR3 1BQ
First published 2001
ISBN 0 7176 1798 X
All rights reserved. No part of this publicationmay be reproduced, stored in a retrievalsystem, or transmitted in any form or by anymeans (electronic, mechanical, photocopying,recording or otherwise) without the priorwritten permission of the copyright owner.
This booklet was prepared by the FoundriesIndustry Advisory Committee and has beenagreed by the Health and Safety Commission.It contains notes on good practice which arenot compulsory but which you may findhelpful in considering what you need to do.
Contents Introduction 1
What is hand-arm vibration syndrome? 2
What are the risks? 2
What are the costs of HAVS to employers? 3
Where is there a risk of HAVS in the foundry? 5
Questions to ask 5
The hierarchy of control 5
Casting design for easy knock-off/cut-off 10
Designing for knock-off 11
Summary 13
Reduction and removal of flash 14
Elimination or reduction of flash by design and
process control 14
Questions to ask 15
Removal of flash 15
Good grinding practice 19
Wheel selection 19
Training 23
Summary 24
Alternatives to conventional abrasive wheel grinding 24
Other management controls 25
Summary 27
Health surveillance 27
References 28
Further reading and information 29
HSE BOOKS
Foundries
Industry
Advisory
Committee
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Hand-arm vibration infoundries
1
This booklet was produced by The Health and Safety
Executive's (HSE) Metals and Minerals Sector in
collaboration with the Castings Development Centre.
The Foundries Industry Advisory Committee (FIAC) and
its Noise and Vibration Subcommittee were consulted
during its production. It is aimed at all levels of
management, safety officers, safety representatives and
others within the foundry industry who may require
guidance on how to reduce the risks of hand-arm vibration
syndrome (HAVS). Sources of guidance on other aspects of
HAVS management which could also be of relevance to
your foundry are listed in the Further reading section.
Introduction
2
Vibration experienced in many foundry processes can
cause a range of disabling health complaints that are known
collectively as 'hand-arm vibration syndrome' (HAVS). The
best known of these is 'vibration white finger' (VWF) which
is caused by the effects of vibration on the body's blood
circulation.
Other damage may be caused to the nerves and muscles of
the fingers and hands causing numbness and tingling,
reduced grip strength and sensitivity. HAVS is a reportable
disease under the Reporting of Injuries, Diseases and
Dangerous Occurrences (RIDDOR) Regulations 1995.1
Studies indicate that around half of all foundry workers
exposed to hand-arm vibration show symptoms of VWF.2
Often, symptoms take several years to develop, but they
may appear after only a few months in susceptible people.
A 1996 HSE study3 found VWF in 25% of a group of
fettlers; a further 11% showed other symptoms of HAVS.
The risk of suffering from HAVS depends on both:
■ the level of vibration to which the individual is
exposed; and
■ the time of exposure (both in terms of hours per day
and years of work).
Hand-transmitted vibration is expressed in terms of the
acceleration of the equipment in contact with the hand.
The figure given is normally given in metres per second
squared (m/s2), eg 2.8m/s2.
An employee’s daily vibration exposure depends upon the
size of this figure as well as the length of time that the
employee is exposed to the vibration.
What is
hand-arm
vibration
syndrome?
What are the
risks?
3
Length of working day in hours 16 8 4 2 1 0.5
Average vibration level (m/s2)
over a workingday to give the 2 2.8 4 5.6 8 11.2
action level of 2.8m/s2 (A8)
What are the
costs of HAVS
to employers?
The aim should be to reduce the amount of exposure of
each employee to as low as is reasonably practicable.
The HSE action level is 2.8m/s2 averaged over an eight-
hour day. Even if exposure to vibration can be reduced to
the level of 2.8m/s2, wherever it is reasonably practicable
to reduce exposure further, then this should be done.
The table below shows the relationship between vibration
and time.
Survey findings4 suggest that 20% of VWF sufferers take an
average of 12 days per year sick leave because of their
condition. Sufferers often make a claim for compensation
from their employers, and settlements can be substantial -
six-figure sums have been paid out. Agreements between
certain unions and insurance companies mean that large
numbers of claims are settled out of court on an agreed
monetary scale. The real costs to employers can be hidden
since they include additional costs such as extra
administration, recruiting and training of replacement staff,
and higher insurance premiums.5
Table 1
Average vibration levels over the working day which cause an average over an 8-hour working day
(often expressed as A(8)) of 2.8m/s2
HSE studies have shown that, just like an iceberg, the true
costs to an employer of failing to manage hand-arm vibration
(HAV) are not always immediately visible.
Key legal duties
Employers have a duty under the Health and Safety at Work
etc Act 1974 to provide and maintain working conditions
and practices that are, so far as is reasonably practicable,
safe and without risks to health. The Management of Health
and Safety at Work Regulations 1996 expand on this general
duty, and require employers to make a suitable and sufficient
assessment of the risk to health (including HAVS) and to
make suitable arrangements to control those risks. This
includes appropriate health surveillance regarding risks.6
In addition, there are further requirements to ensure the
suitability of tools and equipment, and their maintenance,
under the Provision and Use of Work Equipment
Regulations 1998.7
4
Visible costs
Compensation payments,
Absenteeism
Possible hidden costs
Loss of expertise and
experience
Production delays
Overtime working
Temporary labour
Subcontracting costs
Investigation time
Supervisors’ time diverted
Clerical effort
Fines
Legal costs
Insurance premiums
Expenditure on emergency
supplies
£1
Figure 1 Typical costs of HAVS to employers
£8-£36
5
A suitable risk assessment should be carried out to
establish whether there is a problem caused by vibration in
the foundry. Advice on carrying out an assessment is given
in Foundries information sheet No 10 Assessing the need for
action. Where a problem is identified, then action should be
taken to reduce the risk from HAV.
The risk of HAVS is highest in, but not restricted to the
dressing shop. The whole foundry process, from initial
design onwards, should be considered and the following
questions asked:
■ Can the foundry be organised so as to reduce the
exposure of individuals to vibration?
■ Can improved design eliminate or reduce the need
for fettling? This will reduce the risk of HAVS.
Also, since the costs of fettling can constitute
anything up to 50% of the cost of a casting, then a
reduction in the need for fettling can reduce the
overall costs in the foundry.
■ Can the exposure of people to vibration be reduced
by control measures: ie improved, vibration-reduced
tools; better tool selection; and better maintenance
regimes for tools etc?
■ Do employees know how to protect themselves?
In order to reduce hand-arm vibration, you should use the
control measures listed overleaf. Each listed measure
should be examined in turn, and if reasonably practicable,
applied before the next measure is considered. Remember
that not all of the control measures may be applicable or
practicable in your foundry. In some cases, you may need
to apply more than one control measure to achieve an
acceptable reduction in exposure to vibration.
Where is
there a risk
of HAVS
in the
foundry?
The hierarchy
of control
6
The hierarchy of control
1 Elimination
modifying the process to eliminate the need
for the hazardous operation.
2 Substitution
using an alternative operation to achieve the
same aims, but with a lower risk.
3 Engineering controls
reducing the risk from the operation by
engineering means.
4 Management controls
limiting the exposure or risk of exposure by
management techniques.
5 Personal protection
last resort measures if adequate control
cannot be achieved by other means.
(It is of limited application to HAVS.)
7
Elimination
There are three main methods by which fettling can be
eliminated, so reducing exposure to vibration along with
the possible benefits of reducing dust and noise. All need
close co-operation between the different foundry
departments for these solutions to be effective.
■ Design casting and runner systems to allow for non-
manual cut-off/knock-off. Correct positioning of
runners and risers can allow the use of semi-automatic
cut-off machines, knock-off guns, hydraulic wedges or
other non-manual methods (see pages 11 and 12).
■ Control flash by changes in pattern design and
tolerances, binder system, cope/drag alignment
tolerances, clamping/weighting arrangements and wall
thickness/reinforcement (see pages 14 and 15).
■ Produce the casting after knock-off/cut-off in a form
suitable for direct machining.
These approaches to elimination can be fully utilised by
mechanised foundries with long production runs, but some
may be used by jobbing foundries to good effect.
Ask if your customer requires a high
standard of fettling. If not, you can
lower your costs as well as reduce
your employees exposure to vibration.
8
Substitution
With any substitution, it is important to fully assess all
the risks from both the original and proposed new
operations so that the overall benefit can be determined.
Possible solutions include the use of autofettlers,
cropping machines and semi-automatic surface grinders,
which mainly apply to mechanised, long-run foundries.
There may be vibration-reduced alternatives to chipping
and grinding, such as flame cutting (though this can have
the disadvantage of increased fumes), or alternatives to
conventional grindwheels such as belts. Other sections in
this booklet expand upon possible substitution methods.
Engineering controls
Replacing older design fettling machines by newer
machines incorporating 'state of the art' design features
is one option. The features offered by manufacturers are
constantly improving. Ask your supplier for details of
these features and 'in-use' vibration data they are able to
supply.
Retrofitting for your present machinery may be possible,
but care should be taken that it does effectively reduce
vibration and that it is cost effective. Ergonomic
improvements, balancing rigs, using lighter or more
powerful machines, or providing vibration isolated work
rests and hand grips can sometimes be beneficial.
Management controls
There are a number of management controls available
which can help reduce the effects of vibration exposure,
or limit the exposure itself. These include basics like:
■ choosing the right tool for the job;
9
■ establishing a purchasing policy for vibration reduced
tools;8
■ regularly maintaining tools;
■ providing adequate training and supervision to
encourage good fettling practice and prevent wheel
abuse;
■ ensuring that workers in other production areas are
aware of the effects their work has on the fettling
shop;
■ minimising the use of chipping hammers etc, by limiting
their use to assessed specific operations and operating
under a formal 'system of work ' procedure;
■ ensuring that the correct grade or hardness of
grindwheel is used in any grinding operation;
■ providing frequent work breaks and job rotation; and
■ maintaining good temperature control.
More controversial suggestions include:
■ implementing a no-smoking policy to discourage
smoking among fettlers (smoking impairs circulation);
and
■ properly managing piecework systems to avoid unsafe
practices and unnecessary exposure to vibration.
Personal protection
Anti-vibration gloves may have little effect at the most
hazardous frequencies and, in some cases, may increase
the vibration reaching the hand. Warm gloves and clothing
can help reduce vibration by keeping the hands warm and
improving blood flow.
10
The removal of the runner/feeder system (commonly
known as knock-off or cut-off depending on the method
used) and grinding down the resulting stubs are usually
manual operations. They can lead to significant vibration
exposure. Improving the design of the casting and running
system can minimise the effort required to knock-off.
Added benefits of improved design can include:
■ reduced exposure to noise during knock-off;
■ limited exposure to both dust and noise when carried
out prior to shotblasting; and
■ significant savings in handling and fettling costs.
Designing and planning for runner removal
Although the aim is to produce a sound casting, failure to
take other matters into account can lead to problems
later. You should consider:
■ providing an adequate means of handling the casting
during finishing and use; and
■ designing for efficient runner and riser removal.
Knock-off methods
Manual knock-off is used where the metal is sufficiently
brittle, and where in-gates and riser heads can be notched.
Hammering gives significant exposure to impact and
vibration. Knock-off guns or hydraulic wedges can lower
exposure to impact and vibration, but to allow their use
the casting/runner system may need to be redesigned
(especially in the case of hydraulic wedges). For larger
castings, a crane-operated ball knock-off may be
appropriate.
Casting design
for easy knock-
off/cut-off
11
Casting/runner systems should be designed so that the
gates, risers and feeders easily break off just clear of the
casting. This helps prevent break-in as well as minimising
the effort needed for stub removal. It can be achieved by
using breaker cores, Connor block runners, or wide, thin
section in-gates. With small to medium-sized castings it is
likely that the runner system will be detached during any
vibratory or tumble shake-out. Alternatively, removal
should only require a comparatively light tap with a
hammer. The resulting minimal stubs will generally be
amenable to direct machining if positioned appropriately.
As in-gate and feeder size increases, so does the force
needed to remove them. You should consider providing
mechanical assistance such as a knock-off gun (portable or
manipulator-mounted) which 'fires' a rod to remove the
gate or feeder. The casting needs to be designed so that
the gun can actually reach the parts to be removed, and
action needs to be taken to prevent injury from the ejected
part which may travel at high speed in an unpredictable
direction.
Careful design of both casting and runner system can
permit the use of wedges. Both sides of the wedge need
something for the wedge to work against for it to be
successful. Some foundries have designed their own
hydraulic tools for removing runners, although these are
not yet commercially available.
For large castings, a suspended ball - using the principles
seen in building demolition, is sometimes used for knock-
off. Control is difficult and this system requires that the
runner must be well clear of any casting projections to
prevent product damage.
Designing for
knock-off
12
Cut-off methods
Casting cut-off systems are not instantaneous and therefore
they vibrate rather than impact.
Common arrangements include the use of abrasive cut-off
discs mounted on:
■ a pedestal grinder, where the feeder system is manually
pressed against the rotating fixed abrasive disc;
■ a bench-mounted lifting arm (similar to a cross-cut
circular saw fitted with a cutting disc), where the
rotating abrasive disc is pulled down onto the feeder; and
■ a portable straight or angle grinder.
All of the above involve transmission of vibration from the
casting or abrasive wheel to the operator.
By decreasing ingate/feeder size, cut-off time (and so vibration
exposure per casting) can be reduced.
Try to avoid creating long stubs. To minimise employees’
vibration exposure caused by extensive and awkward fettling,
and to minimise possible damage to the casting, the following
design principles should be considered:
■ position runner systems that permit easy access for the
cut-off wheels;
■ avoid locating ingates in casting hollows; and
■ mount the ingate on the joint line of the casting if this
permits the simultaneous removal of both residual stub
and joint-line skim.
The use of remote abrasive cutting using a manipulator or jig
to hold the castings, in conjunction with an automatic or
semi-automatic cut-off wheel, can help reduce exposure as
the operator is not holding either vibrating tool or casting.
13
Using bandsaws on softer metals (eg aluminium) should be
avoided if excessive vibration and noise is experienced.
Thermal cutting operations (eg oxy-gas, arc-air, plasma
cutting) are sometimes used on harder materials. Despite
being largely manual operations, vibration levels are often
comparatively low. Unfortunately, these methods can
introduce the problems of increased fumes and noise
unless rigorously controlled.
Laser cutting or abrasive water jet cutting eliminate
exposure to vibration and should be considered where the
capital costs make them a reasonably practical solution.
Reducing time spent fettling also reduces:
■ the employees’ exposure time to hazardous
vibration; and
■ the cost of a casting.
The following steps can promote efficient knock-off and
cut-off, so reducing fettling time.
1 Determine the components, sizes and position of
the running system required for production of a
sound casting.
2 Examine the options for runner removal, taking into
account their size, position and material.
3 Explore the possibilities for remote operation or
mechanical assistance.
4 Optimise the design of casting and runner system to
allow runner removal by the preferred method and
leaving minimal stubs.
14
Flash is the unwanted penetration of metal into joints of a
mould and can be caused by:
■ poor fit at mould assembly due to excessive tolerances
built in at the pattern design stage;
■ poor pattern making practice;
■ box wear/distortion at the moulding/core making
stage;
■ misalignment caused by poor control of locating
pins/prints etc; and
■ movement or distortion caused by insufficient mould
strength (binder system, cure time, reinforcement).
Flash is the casting 'defect' which leads to most fettling.
Any reduction in flash or its subsequent removal will reduce
exposure to vibration per casting, and save money spent in
unnecessary fettling.
The aim is to produce a sound casting with minimal flash,
and not to produce a poor casting that can be made
acceptable by expensive fettling.
To significantly reduce excessive flashing, all aspects of the
casting process, from initial design to pouring, may need to
be examined. Communication between designers,
moulders/coremakers, patternmakers and fettlers is needed.
They should be aware of how their activities affect others in
the process so that an effective solution can be found.
Reduction and
removal of
flash
Elimination or
reduction of
flash by design
and process
control
A few minutes thought at the designstage can save hours of expensive andhazardous fettling!
15
■ Does the design minimise the need for fettling,
eg minimum number of cores, joint lines accessible?
■ Can a triangular section be designed onto the joint
line to give an aesthetically acceptable joint with
minimal fettling?
■ Are the core/core print tolerances minimised, taking
into account pattern production methods? (CNC
machined patterns should allow tighter tolerances
than handmade ones.)
■ Are core dressers/setters trained to use the
minimum of core rubbing needed to give a good fit?
■ Is the sand/binder system appropriate for this
casting, and well compacted and fully cured?
■ Is the mould reinforcement adequate?
■ Are the mould/core components set firmly to prevent
movement under pressure from the molten metal?
■ Is wall support adequate to prevent break-out?
■ Are locating pins, lugs and prints set accurately to
allow proper alignment?
■ Are the weighting/clamping arrangements adequate
to prevent cope lift?
■ To allow proper alignment and prevent metal
seepage are pattern equipment and core/moulding
boxes in good condition?
■ By modifying the design or casting process can other
defects requiring remedial fettling, such as sand
burn-on, be minimised?
It is unlikely that flash will be completely eliminated,
especially at jobbing foundries, so it is important that its
removal is properly managed.
The method of flash removal should be chosen to minimise
vibration exposure. Since this depends on both vibration
level and exposure time, a method with high vibration
Removal of
flash
16
levels but short exposure times may be better than one
which has lower vibration levels but much longer fettling
times. The fettlers' daily vibration exposure should not
exceed HSE's current action level of 2.8 m/s2 (see Table 1 on
page 3).
Chipping hammers should generally be avoided where
possible because of the high vibration levels produced. If they
must be used, then choose 'vibration reduced' models.
Currently, even some 'vibration reduced' versions can reach
HSE's action level in less than one hour's use. But holding the
chisel, or using conventional chipping hammers, can exceed
the action level in minutes. This type of work should be
given priority for action to reduce vibration exposure.
Depending on the metal being cast, it is often possible to
remove flash in relatively large pieces using manual hammer
blows. While this is the preferred method, the risk of work-
related upper limb disorders (WRULDS) should be managed.
Some foundries that produce castings that are particularly
prone to flash problems are designing a notched 'flash wing'
which can be readily removed with a hammer or detached at
shake-out or shotblast. This may particularly apply to flash
between adjacent cores, which should form a port which can
then be simply rodded through.
The alternatives for removing substantial amounts of flash
include:
■ pincers/nibblers (though care should be taken to ensure
that this does not increase the risk of WRULDs);
■ cut-off wheels and discs;
■ cropping machines (especially on long run production);
and
■ methods such as arc/air (though this may increase the
risks associated with fume evolution and noise).
17
Manual fettling is not the only way of removing residual
waste metal. Automated or semi-automated methods can
reduce employees’ exposure to vibration. These are
usually, though not exclusively, found in larger foundries
producing long runs of a limited range of castings.
Mechanical alternatives include automatic or semi-
automatic cut-off machines, cropping machines and
automatic grinding machines of varying complexity up to
and including a fully programmable robot fettler.
The mechanical alternatives below can save a great deal of
fettling, but their main drawback is the need for repetitive
manual loading/unloading of castings. Ergonomic issues
need to be considered. The benefits of using devices such
as tilting/tipping stillages and magnetic/vacuum handling
devices etc also need to be evaluated.
Automatic or semi-automatic cut-off machines
These consist of an enclosure containing a slitting wheel
and a moveable clamping mechanism to hold the casting
and the runner system. The clamping mechanism is then
moved to apply each runner to the wheel. Such systems
have been used successfully in both long-run and jobbing
situations. But the casting and runner systems must be
designed to allow access of the runners to the wheel to
give minimal stub at cut-off.
Cropping machines
These are small presses used to clip off joint line flash, used
for smaller castings. Dies have to be prepared for each
individual casting type, so this technique is favoured for
long production runs.
18
Manipulators
Manipulators are moveable jigs which either hold castings
against a grindwheel, or hold a grinding tool against a
casting. They are a form of remote manual operation,
usually with a feedback system to the operator to prevent
over-fettling. This technique does not have the set-up
programming problems of other methods and can be
applied to a jobbing situation. Where several grinding
operations are required on each casting, manual handling
can be considerably reduced. Manipulators could be
particularly beneficial to jobbing foundries which have an
identified HAVS problem.
Automated grinding stations
These can range from automatic single operations without
programming through to a full robot fettler which can
pick-and-place and carry out a range of grinding
operations. A range of simpler (and cheaper) autofettlers
to cover the range of castings produced are more
commonly used. Common applications include:
■ Machines for peripheral grinding of cylindrical or
circular castings. They consist of an in-belt and out-belt
with fettling station between. Castings are clamped on
a central indexing point and spun against a grindwheel.
■ Carousel-type machines. Small castings are fitted to a
rotating jig, and the exposed sides ground flat. Finished
castings are discharged to belt or stillage.
■ Straight-through machines. Larger castings such as
cylinder blocks or heads are usually presented and
discharged on a belt and have one or two faces
ground flat.
■ Jigs. They are used with a conventional pedestal
grinder, they hold the casting while traversing across
the wheel.
19
Poor grinding practice increases the risk of HAVS. To
ensure good grinding practice choose the right tools for
the job and proper training for the fettler.
Tool selection
Grinding machines should be selected to effectively
remove the material to be ground off. Grinders with built-
in vibration reduction are preferred.
An advance in grinder vibration reduction is the recent
development of automatic spindle balancing (ASB). Field
research has shown that angle grinders fitted with ASB can
generally be operated for a full shift without the HSE
action level for vibration being exceeded.
In the case of pedestal grinders, efforts have often been
made to isolate the work rest from being affected by the
grinding vibration by mounting it independently from the
machine. Potentially, vibration reduction can be achieved
but this is not always successful.
Choosing the correct type of grinding wheel can reduce
noise, dust and vibration as well as reducing fettling costs.
Too hard a wheel will rapidly lose cutting efficiency and
lead to unnecessary vibration exposure (see Table 2).
The nature of the grindwheel is specified by a series of
numbers and letters together with further codes defining
the shape, size and fittings.
Good grinding
practice
Wheel
selection
20
The wheel specification code consists of four parts,
eg A14 QB, namely:
A an alphanumeric code denoting the type of
abrasive, eg A-alumina, 63A - zirconia mixture.
14 a number denoting abrasive grain size - for most
fettling operations this will be in the range 12-36.
Q a letter denoting the 'hardness' or grade ranging
from E (soft) to Z (very hard).
B a letter or letters denoting the bond type - for
fettling this will usually be B for resinoid and/or
possibly BF for reinforced resinoid.
Wheel hardness
Harder material to be ground will generally require alumina
abrasive, finer grit size and softer grade; while soft
materials may need silicon carbide abrasive and will need
coarser grit and harder grade wheels. High stock removal
rates generally need coarser grit and harder grade wheels
with a high power machine.
As far as managing HAVS is concerned, a critical factor for
a particular fettling operation is the hardness. The cutting
wheel should ensure that as abrasive particles have their
cutting points worn away they are released from the wheel
matrix and new sharp-edged particles are exposed. If too
soft a wheel is used then abrasive particles are removed
from the wheel surface before they have lost their cutting
edges, which is wasteful. When too hard a wheel is used
(a much more common situation) then there may be more
serious consequences, as described overleaf.
21
Consequences of using too hard a wheel
It is a false economy to use a wheel that is too hard (see
Table 2). Although wheel life is extended, the worn-down
abrasive particles remain firmly bonded to the wheel
surface and the surface of the wheel becomes polished
(known as glazing). Because the wheel no longer cuts
efficiently the time taken to fettle a casting is greatly
extended.
Glazing causes 'skipping' of the casting against the wheel.
This causes lobing of the wheel, which is difficult to dress
out. There is some evidence that skipping causes relatively
high levels of impulsive vibration, an important factor in
causing HAVS. The lack of cutting action can lead fettlers
to use undue pressure or abuse the wheel by impacting the
wheel against the casting (or vice versa) to try to achieve
some cutting. At best this leads to further wheel distortion
and greatly increased vibration exposure and at worst to
wheel breakage, which can have very serious
consequences.
Alternatively, (and less frequently because it takes time)
fettlers will dress off the worn abrasive, often reducing the
wheel life unproductively. In any case, the net result is
greatly increased fettling times per casting, with
consequent longer exposure to dust, noise and vibration
and unnecessary fettling payments.
On changing to a free-cutting wheel of the correct grade, it
is not unknown for the wheel to fettle two and a half times
the number of castings even though it lasts only half as long
as a wheel that is too hard. There is, therefore, a net
productivity increase per wheel and a greatly reduced
fettling time per casting, which results in lower fettling
costs per casting.
Too soft a Optimum Too hard a wheel wheel wheel
Wheel Short life Maximum metal Apparent long performance removal rate life,
BUT
If very soft it Minimum Will glaze and may not cut fettling per stop cutting at all casting after a while
Health Minimum Long exposure effects exposure to to vibration
vibration per casting Long noise
exposure per casting
Long exposure to dust per casting
Long-term HIGH OPTIMUM HIGHcosts
due to due to
Short life Failure to fettle Possible efficientlyscratching Possible wheelof casting abuse and
breakage by fettlers
22
Differing grades for different operations
Unfortunately, because of the effects of wheel surface
speed, feed force and contact area, this selection process
should be carried out for each type of grinding machine in
use and ideally for each type of grinding operation.
However, where the same machine/wheel combination is
used for a range of different types of operation and/or
casting size, then clearly a compromise must be made.
Table 2 Wheel hardness selection
✘
✘
✘
✘
✘
✘ ✔
✔
✔
✔
✔
✘
✔
✘
✘
✘
✘
✘
✘
✘
23
There can be differences in the feed forces used by different
fettlers; about one grade difference could result for an
optimum wheel. When considering wheel hardness, the best
wheel for 'average' fettlers should be selected to avoid
extremes. Compromise should favour softness to ensure
that the wheel remains free cutting. Note that the actual
grade letter used to indicate bond strength may vary slightly
between different suppliers.
This advice is particularly relevant to abrasive wheels, but
most comments will also apply to abrasive coated discs
and/or belts used in fettling departments.
Sufficient training should be provided for fettlers to know
how to select the right machine for each job, and how to
use it correctly. If a fettler is to mount wheels, then adequate
training is required under the Provision and Use of Work
Equipment Regulations 1998.7 Additional training may be
required if a job changes substantially. Learning from other
colleagues is unlikely to be the best form of training.
Common bad practice:
■ Impacting castings on wheels (or vice versa) is a
dangerous practice which could lead to wheel
breakage. The practice originates from using a wheel of
too hard a grade which rapidly loses cutting efficiency.
Instead, grinding should generally be carried out with a
smooth, steady pressure to avoid sudden loading.
■ Grinding on the sides of edge grinding wheels and
stopping wheel rotation by applying the wheel to, say
the grinding bench, are poor practices - these can lead
to undue stresses in the wheel that it is not designed for.
Training should be supported by adequate supervision to
ensure that competency has been reached and maintained.
Training
24
Alternatives to
conventional
abrasive wheel
grinding
Grinding wheels should be selected for maximum
cutting efficiency and not maximum life, as is often
currently the case. In conjunction with other
approaches to HAVS reduction this should significantly
reduce exposure, limit dust and noise, and give cost
savings per casting.
There are some alternative grinding techniques that
effectively eliminate the problems associated with out-of-
balance wheels and discs, although there could still be
resonance effects. They should be considered as part of a
HAV control programme.
Abrasive belts
Abrasive belt fettling is a well-established technique which
normally exposes the operator to less vibration than
conventional abrasive wheel grinding. It is frequently seen
in finishing fettling such as the final joint line skim, which
might involve a small portable linisher. Larger belts can be
used for initial rough dressing.
Metal burrs
Equally well established is the use of metal burrs or rotary
files instead of stone points for interior or fine fettling.
Because the abrasion is only at the surface of the tool the
potential for becoming out of balance is reduced. Excessive
sideways forces on these relatively small tools can cause
the shaft to bend, resulting in increased vibration. The
burrs should be replaced if there is any evidence of this
occurring.
25
Impregnated steel wheels
A recent development is the use of steel wheels with a
relatively thin layer of nickel impregnated with a very hard
abrasive such as diamond or cubic boron nitride on the
edges or sides as appropriate. This abrasive layer is very
hard wearing and can last many times longer than
conventional wheels. Because of its construction, there is
little potential for the wheel to become unbalanced, so in
theory, it should vibrate less than conventional wheels.
This is still to be tested in practice.
There are other techniques which can be used to reduce
an employee’s exposure to vibration or minimise its effects
on health.
Economic and health and safety benefits can be gained by
improved inter-departmental co-operation. Better
communication can lead to the production of quality
castings which require minimal subsequent fettling.
Careful consideration should be given to piecework and
other incentive schemes to ensure that the exposure of
fettlers to vibration is not excessive.
Work organisation
■ Job rotation may help to reduce the period of
exposure to vibration. (In practice, this may be difficult
in a foundry because many of the other jobs available
may also expose the worker to vibration.)
■ Frequent breaks may help. Long periods of exposure
to vibration should be avoided; short bursts of activity
are better.
■ Mixing tasks within a job may help to prevent fatigue.
Other
management
controls
26
Pre-work warm up
Ensuring good blood circulation is important. Possible
approaches could include spending a few minutes carrying
out suitable exercises, immersing hands in warm water or
using a warm air hand dryer prior to starting work. (These
procedures can be also used after breaks.)
Keeping the hands warm
It is advised that work is carried out where the ambient
temperature is adequate. Warm clothing and gloves can be
beneficial. The cooling effect of exhaust air from pneumatic
machines can be minimised by directing the exhaust air
away from the workers’ hands. This is often best achieved
by fitting an exhaust tube and leading it back along the
supply line.
Discouraging smoking
Smoking affects blood flow, so a reduction in smoking just
before and during working may help. Smokers should be
made aware of the relationship between smoking and
HAVS.
27
Where practicable, the need for grinding should be
eliminated or reduced by good design and control of
the casting process.
Residual metal should be removed by non-manual
methods where possible.
The remaining manual grinding should be carried out
using good grinding practice and vibration-reduced
tools including:
- choosing the correct grinding machine;
- choosing the correct grinding wheel for the job;
- training;
- supervision;
- steady grinding pressure;
- avoidance of wheel abuse; and
- providing a good working environment, including
temperature control.
HSE recommends health surveillance for workers who are
regularly exposed above 2.8 m/s2. Health surveillance will
not prevent injury in the way that control measures
outlined in this leaflet will, but it can be used to detect
early signs of injury and prevent significant handicap.
Detailed advice on health surveillance is given in HSE
publications Surveillance of people exposed to health risks at
work8 as well as in Hand-arm vibration9 and Health
surveillance in the foundry industry.10
Health
surveillance
28
1 RIDDOR explained HSE31(rev1) HSE Books
1999 (single copy free or priced packs of 10
ISBN 0 7176 2441 2)
2 Griffin MJ Handbook of human vibration Academic Press
1996 ISBN 0 12 303041 2
3 Bednall AW and Pitts P 'Exposure to hand-arm
vibration in foundries' Foundry trade journal March 1996
4 Hodgson J, Jones J, Clegg T Self-reported work-related
illness in 1995 Research Report HSE Books 1998
ISBN 0 7176 1509 X
5 The costs of accidents at work HSG96 (Second edition)
HSE Books 1997 ISBN 0 7176 1343 7
6 Management of health and safety at work. Management
of Health and Safety at Work Regulations 1999.
Approved Code of Practice and guidance L21 (Second
edition) HSE Books 2000 ISBN 0 7176 2488 9
7 Safe use of work equipment. Provision and Use of Work
Equipment Regulations 1998. Approved Code of Practice
and guidance L22 (Second edition) HSE Books 1998
ISBN 0 7176 1626 6
8 Health surveillance at work HSG61 (Second edition)
HSE Books 1999 ISBN 0 7176 1705 X
9 Hand-arm vibration HSG88 HSE Books 1994
ISBN 0 7176 0743 7
10 Health surveillance in the foundry industry IACL104
HSE Books 1998
References
29
Vibration solutions: Practical ways to reduce the risk of hand-
arm vibration injury HSG170 HSE Books 1997
ISBN 0 7176 0954 5
Health risks from hand-arm vibration: advice for employers
INDG175(rev1) HSE Books 1998 (single copy free or
priced packs of 10 ISBN 0 7176 1553 7)
Health risks from hand-arm vibration: advice for employees and
the self-employed INDG126(rev1) HSE Books 1998
(single copy free or priced packs of 15
ISBN 0 7176 1554 5)
Buying new machinery INDG271 HSE Books 1998 (single
copy free or priced packs of 15 ISBN 0 7176 1559 6)
Hazards associated with foundry processes: hand-arm vibration
- assessing the risk Foundry Information Sheet FNIS10
HSE Books 1999
Power tools: How to reduce vibration health risks. Guide for
employers Leaflet INDG338 HSE Books 2001(single copy
free or priced packs of 15 ISBN 0 7176 2008 5)
Video: Hard to handle hand-arm vibration: managing the risk
HSE Books 1998 ISBN 0 71716 1881 1
CD-ROM: The successful management of hand-arm vibration
HSE Books 1999 ISBN 0 7176 1713 0
While every effort has been made to ensure the accuracy
of the references listed in this publication, their future
availability cannot be guaranteed.
See inside back cover for details of how to order HSE
publications and products.
Further
reading and
information
Printed and published by the Health and Safety Executive09/01 C30
This booklet was prepared by the Foundries Industry Advisory Committee andhas been agreed by the Health and Safety Commission. It contains notes ongood practice which are not compulsory but which you may find helpful in
considering what you need to do.
30
9 780717 617982
I S B N0-7176-1798-X
Price £6.00